1. Field of the Invention
This invention relates to inks, and in particular aqueous inks comprising water insoluble dyes.
2. Description of Related Art
Dyes in some aspects are superior to pigments in ink jet inks for a number of well-known reasons. Pigment particles are about a million times larger than dye molecules. Pigment based inks are, basically, finely ground particles suspended in a transfer medium. The much smaller dye molecules may, under the appropriate conditions, dissolve in a medium as compared with mere physical suspension. It is well known that, owing to its molecular characteristics, dye produces colors spanning a broader range, colors which are truer or otherwise more reproducible, and colors of greater strength. However, water soluble dyes smear and fade after printing. Smearing and fading are, in most applications, highly undesirable characteristics and present severe limitations on the usefulness of dye inks in everyday printer use.
What is still needed is one or more water insoluble dyes dissolved in an aqueous-based ink vehicle. This dye-based ink would enable a greatly expanded range of water-fast, non-smearing, highly saturated colors with high reproduceability and long shelf life. The ink composition of the present invention is useful in ink jet printing, enabling color consistency over a broad range and suitable, owing to non-smearing and non-fading properties, for archival purposes.